Started Rust in Action MEAP.

1 files changed, 42 insertions, 0 deletions

diff --git a/meap/meap-code/ch3/ch3-not-quite-file-2.rs b/meap/meap-code/ch3/ch3-not-quite-file-2.rs
new file mode 100644
index 0000000..f4f86fd
--- /dev/null
+++ b/meap/meap-code/ch3/ch3-not-quite-file-2.rs
@@ -0,0 +1,42 @@
+#![allow(unused_variables)] // <1> Silences a warnings caused by `open()` and `close()` not making use of needing their argument

+

+#[derive(Debug)] // <2> This enables `File` to work with `println!` and its `fmt!` sibling macros, used at the bottom of the code listing

+struct File {

+  name: String,

+  data: Vec<u8>,

+}

+

+fn open(f: &mut File) -> bool { // <3> These two functions will remain inert for now

+  true 

+}

+

+fn close(f: &mut File) -> bool { // <3>

+  true

+}

+

+fn read(f: &File, save_to: &mut Vec<u8>) -> usize { // <4> Return the "number of bytes read"

+  let mut tmp = f.data.clone(); // <5> Make a copy of the data here, as `save_to.append()` will shrink the input vec

+  let read_length = tmp.len();

+  save_to.reserve(read_length); // <6> Not strictly necessary, but useful to know about

+  save_to.append(&mut tmp); // <7> Allocate sufficient data in the `save_to` buffer to hold the contents of `f`

+  read_length

+}

+

+fn main() {

+  let mut f2 = File { 

+    name: String::from("2.txt"),

+    data: vec![114, 117, 115, 116, 33],

+  };

+

+  let mut buffer: Vec<u8> = vec![];

+

+  open(&mut f2);                          // <8> Do the hard work of interacting the the file.

+  let f2_length = read(&f2, &mut buffer); // <8>

+  close(&mut f2);                         // <8>

+  

+  let text = String::from_utf8_lossy(&buffer); // <9> Convert `Vec<u8>` to `String`. Any bytes that are not valid UTF-8 are replaced with �

+

+  println!("{:?}", f2);

+  println!("{} is {} bytes long", &f2.name, f2_length);

+  println!("{}", text) // <10>  View [114, 117, 115, 116, 33] as an actual word

+}
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